A solenoid actuated valve assembly operates to inject fuel into an internal combustion engine. To actuate the valve, a magnetic circuit must be established to attract the valve armature to lift the valve off the valve seat. There must be a closed loop of adjacent magnetic components encircling the coil, except for the small working air gap across which the valve assembly armature travels. To satisfy this requirement for a closed loop about the coil, the components may have to be configured in complex geometries which increase manufacturing costs.
For efficient and accurate operation of fuel injection, it is desired to center the valve assembly concentrically within the injector body to ensure axial motion of the valve with respect to the body and the valve seat. In order to achieve this goal, it is preferable for a valve guide to be in direct contact with both the valve and the inner surface of the injector body to ensure concentricity therebetween.
It is also important that the solenoid coil be free of fuel contamination to assure reliable performance. Over time, fuel may degrade the coil windings resulting in reduced injector performance. A known option is to employ hermetic welds between the components encircling the coil to prevent fuel seepage into the coil. The disadvantage of hermetic welds is the increase in assembly costs.